It’s hard to imagine that the air we breathe is even more polluted inside the house than outside, even in town! And yet … Furniture, paints, floor coverings, household appliances, and even cleaning products reject many chemical molecules in the air. Pets, dust mites and molds also produce allergens, not to mention bacteria and viruses that spread infections.
Our interior contains hundreds of pollutants. According to the Indoor Air Quality Observatory (OQAI), all the homes tested were contaminated with formaldehyde, a molecule classified as carcinogenic, and some at doses above the threshold value set by the World Organization for health (0.12 mg / m3).
The problem ? Chemical particles, allergens, molds, but also humidity or dryness of the air can promote or worsen respiratory problems.
To respond to these concerns, manufacturers are promoting models of air purifiers capable of filtering chemical pollutants, but also of destroying bacteria and viruses. Often very sophisticated, these devices are attractive to both individuals and professionals, such as doctors or traders. What are they worth? Are they effective against viruses?
Air purifiers with filters
These devices work with a mesh of filters: a pre-filter to capture large particles, such as dust and animal hair, an activated carbon filter to stop gases and volatile organic compounds (VOCs) emitted by cigarette smoke, household products, exhaust gases or construction materials (such as benzene or formaldehyde), and a HEPA filter (High efficiency on air particles) which blocks fine particles.
The most common, PM 2.5, is effective on most allergens, certain bacteria or particles from automobile traffic. To claim an action on viruses, the model must have a finer filter called PM 0.1.
“The presence of a very effective HEPA filter can theoretically stop the coronavirus or the H1N1 influenza virus”, indicates Dr. Fabien Squinazi, biologist. The devices are usually tested in the laboratory.
Benefits : they are found at all prices, from € 15 to € 700, and for all uses. They generally cover an area between 5 and 150 m2.
The inconvenients : there can be big differences in efficiency between models, but also between claims made by manufacturers and reality. In addition, pollutants accumulated in the device can be released when a filter is removed for cleaning. Finally, some devices emit a somewhat noisy hum (50 dB).
Ionization air purifiers
These purifiers send ions that stick to airborne particles and amalgamate them. They are sucked in by the device or fall on the floor and furniture. They must then be vacuumed with a vacuum cleaner equipped with a HEPA filter. Ionization mainly targets chemical particles, but some devices also claim a germicidal action.
Benefits : the ions improve the efficiency of the filters in the device. The Blueair brand, which has patented a system coupling ionization with HEPA or activated carbon filters, has seen its devices certified by the American association of domestic appliance manufacturers. This label is a guarantee of quality.
The inconvenients : it is difficult to know how many ions actually come into contact with airborne particles. Furthermore, this type of purifier does not eliminate pollutants : they must be collected with a vacuum cleaner equipped with a HEPA filter.
If one chooses this technology, it is better to turn to models accompanied by a study of efficacy and harmlessness, guaranteeing the absence of ozone emissions.
In 2017, the French Agency for Sanitary Safety (ANSES) report on the effectiveness of purifiers showed great variability in the models tested. The action on bacteria and viruses is also not demonstrated.
Another weakness: ionization can emit ozone into the air. Irritating in particular to asthmatics, ozone is also likely to react with other indoor air pollutants to form new chemical particles.
Ultraviolet air purifiers
These devices contain tubes emitting UVC radiation. This ultraviolet light destroys bacteria and viruses by blocking the replication of their genetic material.
The technology is known to disinfect, for example, surgical equipment. On the other hand, there is no study of the effectiveness of air purifiers using ultraviolet tubes. “You have to be sure that the germs stay in contact long enough with the tubes to be destroyed, otherwise they go in and out of the purifier, “says Dr Squinazi.
Air purifiers by photocatalysis
The aspirated air passes through a filter lined with titanium dioxide tubes. They destroy polluting substances under the effect of UVC radiation to transform them into water vapor and carbon dioxide. Photocatalysis therefore destroys chemical particles, as well as bacteria and viruses.
Benefits : the process was developed by a team from CNRS in Strasbourg. It destroys bacteria, viruses and chemical particles, including 80% to 90% of the toughest, such as carbon monoxide or acetone.
The inconvenients : it is imperative to follow the instructions for use, otherwise the photocatalysis reaction may emit chemical compounds, in particular formaldehyde. The manual is complex: some filters must be changed every two weeks, others washed every month, or replaced once a year… It seems difficult to follow these indications to the letter.
“Carried out in real conditions, the tests showed a very variable effectiveness according to the models”, explains the biologist. The result is difficult to predict because it depends on the arrangement of the filters and the mounting of the purifier: the slightest leak reduces the efficiency of the device.
ANSES emphasizes a risk of chemical emissions (formaldehyde) in the air.
4 purifiers on the test bench
These models are able to filter particles the size of viruses.
Philips AC 2729/10
It contains a pre-filter, a HEPA filter that filters particles down to 0.003 microns and claims action on viruses, an activated carbon filter.
- Capacity: maximum speed of 250 m3 / h, for a room of 65 m2 maximum.
- Its plus: it doubles as a humidifier.
- Price: € 399.
Rowenta Intense Pure Air Connect XL
It contains a pre-filter for large particles, an activated carbon filter and Allergy +, for allergens, fine particles.
- Capacity: maximum speed 360 m3 / h, for a room of 140 m2 maximum.
- Its advantages: a filter dedicated to formaldehyde, an app to connect the device …
- Price: € 431.99.
Dyson Pure Cool Link, purifier and ventilator
It contains a double activated carbon filter and HEPA PM 0.1 which filters out microscopic pollutants.
- Capacity: maximum speed 290 m3 / h, maximum efficiency, for a room of 27 m2.
- Its advantages: the app, the ventilator function, the efficacy test carried out by the Institut Pasteur de Lille on the influenza virus.
- Price: 599 €.
HealthPro 150 IQAIR
It contains 2 filters that combine the qualities of a pre-filter, activated carbon and a HEPA filter with an action on bacteria and virus particles down to 0.003 microns.
- Capacity: maximum speed 350 m3 / h, for a room of 65 m2 maximum.
- Its plus: a very efficient filtration system.
- Price: € 1,099.
Plasma purifiers essentially remove chemical pollutants. But they can generate the formation of secondary pollutants, in particular ozone.